2023 CT5 V Blackwing oil issue

[Artgluck99]

Trying to decipher the code here. When you first picked the car up, there were 8 miles on it after the oil change and then you drove it for 1080 miles for a total of 1088 miles the moment the oil light went on. That was the very first time you checked the oil. The engine was essentially at operating temperature (15 minutes after engine off). Since then after 68 miles 4 qts of oil have been added. There are a number of variables going on, and I suspect the likely answer is you may have been somewhat low (nowhere near 2 quarts or 4 quart) in combination with inexperience at using your dipstick properly. Losing nearly half the oil capacity seems very unlikely without some evidence of smoke out of the tailpipe or dripping on the ground.

Hi Rubberduck, this is the conclusion post to all of this but I appreciate your response so Ill explain. Bought the car with 20k miles on it, part of their final service before pickup was on oil change (I have the work documents). I did not check the oil when I picked the car up. I drove the car 1080 miles then the low oil screen came on. To get the oil level back on the dipstick I had to add 2 1/2 quarts. I drove the car 68 miles home. I then had to add another quart once I got home because the oil was off the dipstick again. I then had the car towed to the dealership in an abundance of caution. The dealership contacted GM and started an oil consumption case. They did 3 oil changes, drove the car for approx 350 miles and measured the oil around 100 miles. They did not see any oil consumption. I have the receipts for the oil I had to add, I posted a picture at the top of this thread showing the dipstick after the 68 miles drive when I got home After adding the 2 1/2 quarts before that drive. I have no idea what happened, if it isn't burning oil I think the only logical conclusion is that it was low when I picked the car up. Hopefully there wasn't any damage done with the low oil level. With all of that said, the dealership was fantastic. They took everything seriously, offered to pay for the oil I had to add Etc. They did the 3 oil changes, had staff drive the car obviously and detailed the car before returning it. Their staff communicated through the entire process, and their staff were all very competent compared with other brands I have dealt with through the years. The car is under the OEM warranty and I have an extended factory until 2031. I will be checking the oil in 500 miles intervals for a while, and definitely after any oil change I have done.

 

[rubberduck]

I’m around 0.5qt low every year when I change my oil. That’s about 2500 miles each year. I don’t baby the throttle.

Even if you used 0.5qt in 1080 miles, that would mean you started out with 6 qts (that coincidentally is what you would put in a V6). I don’t trust the dealership to do anything and I always check all the work when I get back home. I avoid the dealership except for warranty work.

What’s surprises me is with 3 quarts low the oil indicator light did not come on from the very beginning. Did you ask them when they would expect the low oil indicator light to come on? I guess it’s about the time the engine is about to blow.

The other possibility is you started out with 9 qts and your cars burns oil like crazy. However, that seems unlikely if you’re not noticing any smoke.

 

[NorCal Blackwing]

My suggestion having experienced something similar. Ask your dealership to do an oil consumption analysis. They will fill it to the proper level and verify. Then you come back after 1000mi, they measure it, fill to the proper level, and you check again in another 1000mi.

Mine would go from full and verified to low oil warning in about 900 miles of regular driving, which was just within the range GM deems acceptable.

 

[rubberduck]

My suggestion having experienced something similar. Ask your dealership to do an oil consumption analysis. They will fill it to the proper level and verify. Then you come back after 1000mi, they measure it, fill to the proper level, and you check again in another 1000mi.

Mine would go from full and verified to low oil warning in about 900 miles of regular driving, which was just within the range GM deems acceptable.

How many quarts low when your oil warning light came on?

 

[NorCal Blackwing]

How many quarts low when your oil warning light came on?

They told me it comes on when the oil is one quart down, which seems conservative if true.

 

[Artgluck99]

I checked the oil after driving 1,100 miles since they did the oil consumption testing (8/7/2026). There was ZERO oil on the dipstick.

 

[Artgluck99]

This is the picture after I added 1 quart

 

[vagabond]

I didn't see anyone suggest checking the rear of your block. Either the left and right rear head areas or main seal and transmission area. Do you ever smell oil when starting the car or after an oil change?

Also read through this: Is my (5V BW) oil consumption reasonable or concerning?

 

[Artgluck99]

Thanks vagabond, I read your thread. The person who commented about increased oil consumption at 20k miles was probably the closest sitution to mine. I am roughly averaging 2-2 1/2 quarts every 1k miles. It's concerning. The dealership has taken it in for a second time, they said they are going to work with a GM engineer. They may have to drive the car 1k miles to see if the same issue occurs. I signed the paperwork and picked it up on 6/29/26, I bought it from this dealership because it was listed for sale as a CPO car from a reputable Cadillac dealer. Every mechanic I talk to, every car enthusiast I talk to gets quiet and makes a face when I show them pictures of the dipstick, and the slow creeping oil mark as each quart has been added and the new level is checked. The suburu mechanic yesterday said, "I'm really sorry, have they offered you a new engine yet"

I absolutely love the car, and I can never see going back to a soulless bmw or audi or mercedes. I would be willing to buy a new Blackwing as long as the dealership wasn't going to mark it up. They already made money on my GT500 I traded in, and they made money on this car. I am making a car payment on a car I don't have. I am 6'4", so cars for me are not as simple as other boys and girls. I can't fit in any Corvette, I traded my gt500 for this car because I like the sleeper aspect and the manual is a must. I don't think there is anything else out there that does what the Blackwing does. The M5 M4 M3 are like driving computers. I drove a 3 and 4 auto and manual, I really don't understand the popularity. The Blackwing is the way. For those of you who read this far, and have had issues with cars that required dealer or corporate intervention my questions are below. Has anyone had to go the Lemon law path? Has GM (I dealt with GM in 2011 with a truck and it was a nightmare for 8 months) gotten any better at dealing with customer issues? This car is under full OEM warranty until May 2027 then an extended GM warranty until 2031

-What if they claim it hasn't lost enough oil to outside of an acceptable range? Do I attempt to go down the lemon law path?

-They offer to do an engine replacement? Does that crater the value of the car? Can a car be reliable after having an engine replaced?

-If they replace the engine should I push them to put a new clutch in? That would mean 1,400 miles would have been driven by random staff members.

-If they offer to replace the engine should I expect them to add anything to the warranty?

-Should I make an issue of the miles being added during all of this testing and the reduced value of the car?

-Should I get a quote on a new car? See if they will do a buyback and quote a new car?

I am at a loss on this one, this is a very expensive car (to me) and it's all very stressful (yes, first world problem I know). I have bought 1 Kenworth, and multiple Chevy, Dodge, Fords, Toyotas, Hondas, BMW over the past 12 years for my company. I have had issues with vehicles but literally nothing like this. I've had diesels gel, Ford gas trucks that had all sorts of engine issues, but the problem was usually obvious and the dealerships would take care of it.

 

[Merlette]

Really sorry to read what you’re going through. I can only answer some of your very valid questions.

Lemon law in general, and on used cars specifically, varies by state jurisdiction. Cali used to have some of the broadest protection that included used cars, but a court ruling earlier this year nixed that. I believe there are Federal-level protections, but I am not familiar with them.

As far as engine replacement diminishing value, I can only offer a single data point: it doesn’t seem to have in my case. I replaced the engine in my V2 about 4 years ago and the trade in offer for the 5BW I have on order is right in the middle of KBB private party estimates (subject to direct appraisal, of course). The car was long past any extended B2B warranty, but the engine itself came with a 1-year/don’t remember the mileage warranty.

A gallon of oil has no place to hide. There’s only so much that could bypass the pan and not be dripping off something unless…it’s going out the tailpipe.

That much oil should be wreaking all kinds of havoc with the plugs, O2 sensors, and cats, but sometimes you just gotta apply Occam’s Razor. They should have done visuals on all of those parts, even in the absence of DTCs out the wazoo.

Your dealer saying they may have to keep her and put on a 1,000 miles just to prove what you have been telling them smells like BS to me. So as they witness the oil level dropping like a 2-stroke, what then? How does that help get to the root cause? They/GM should be running an exhaust gas analysis (sniffer) test, which should produce positive or negative results in less than an hour.

Good luck! I hope GM does the right thing for you.

 

[Artgluck99]

Really sorry to read what you’re going through. I can only answer some of your very valid questions.

Lemon law in general, and on used cars specifically, varies by state jurisdiction. Cali used to have some of the broadest protection that included used cars, but a court ruling earlier this year nixed that. I believe there are Federal-level protections, but I am not familiar with them.

As far as engine replacement diminishing value, I can only offer a single data point: it doesn’t seem to have in my case. I replaced the engine in my V2 about 4 years ago and the trade in offer for the 5BW I have on order is right in the middle of KBB private party estimates (subject to direct appraisal, of course). The car was long past any extended B2B warranty, but the engine itself came with a 1-year/don’t remember the mileage warranty.

A gallon of oil has no place to hide. There’s only so much that could bypass the pan and not be dripping off something unless…it’s going out the tailpipe.

That much oil should be wreaking all kinds of havoc with the plugs, O2 sensors, and cats, but sometimes you just gotta apply Occam’s Razor. They should have done visuals on all of those parts, even in the absence of DTCs out the wazoo.

Your dealer saying they may have to keep her and put on a 1,000 miles just to prove what you have been telling them smells like BS to me. So as they witness the oil level dropping like a 2-stroke, what then? How does that help get to the root cause? They/GM should be running an exhaust gas analysis (sniffer) test, which should produce positive or negative results in less than an hour.

Good luck! I hope GM does the right thing for you.

Thanks for the reply. Everyone I explain the situation to is interested at first then usually skeptical by the end because nothing makes sense. That's why I started taking pictures of everything, keeping the empty oil bottles etc. I put a white cloth in the exhaust, it is black and dirty but I wouldn't say it had any goo just firm carbon type buildup. Exhaust smells fine, and there isn't any noticeable smoke at all. I am concerned that the previous owner got rid of the car at 20k miles, and had fully PPF the car before they got rid of it. Obviously it is pure speculation but I have to wonder if they discovered this issue and just said goodbye to the car. The dealership had multiple mechanics look at the car, I put fresh cardboard under it for several days. No one found any oil leaking at all.

 

[NorCal Blackwing]

I don't see why the dealership needs to put the 1K miles on. They just need to take a measurement three times (once every 1k miles) - and if the average consumption is out of the range that GM specifies the dealer is empowered to take the investigation further, up to and including engine replacement. When my oil consumption analysis was happening, I would just bring it in myself every thousand miles, and I'd keep a quart of oil and a funnel in the trunk for emergencies.

I doubt you'll be able to lemon-law it over this unfortunately, and if you trade it you'll definitely lose out on some cash, so it might be best to persist through the process. Make sure they give you a copy of the documentation that explains GM's allowable limits as well as the measurements they are taking.

 

[Artgluck99]

Dealership did not end up putting miles on the car, instead they did a compression test which came back fine. Now they are doing a bore scope to check cylinder scoring and the piston rings. Does anyone know if this all makes sense for the issue I'm experiencing?

 

[RDATLTE]

Dealership did not end up putting miles on the car, instead they did a compression test which came back fine. Now they are doing a bore scope to check cylinder scoring and the piston rings. Does anyone know if this all makes sense for the issue I'm experiencing?

IMO, yes. It's a process of elimination. As was stated upthread, the oil has to be going somewhere. Either leaking externally or, being burned internally and ultimately coming out of the exhaust.